Our Ōtautahi-Christchurch Urban Forest Plan provides a long-term vision and strategy to maximise the health and sustainability of the city’s urban trees and forests and the benefits we receive from them.
Christchurch is a green city with a resilient, sustainable and healthy environment where a mix of native and exotic plant communities reinforce the Garden City identity and supports local biodiversity.
Trees provide a range of social, environmental, cultural ecological and economic benefits and services that enrich the quality of urban life:
Our Urban Forest Plan sets out how we will grow our tree canopy and sustain a thriving urban forest of healthy, diverse and resilient trees. It sets our direction and priority for planting, nurturing and protecting our city’s trees for now and the future.
This plan explains how we’ll increase our urban forest and achieve its four goals:
The plan outlines a range of actions we need to take to achieve these goals. These actions will be funded through the Council’s annual and long term planning processes.
Canopy cover is used as a measure to determine the amount of land which is covered by trees. This is done through the use of aerial photography and light detection and ranging (LiDar).
Christchurch City Council has commissioned two surveys to date. One based on aerial imagery taken in 2015/2016 and the second in 2018/2019:
Our city's trees are living breathing parts of our community. They bring us shade in the warm months, shield us from the cold in the winter, and provide fresh air for us to breathe all year.
Development and urban intensification add to transport-related greenhouse gas emissions by increased traffic volumes and contribute to rises in urban heating and stormwater runoff by increased amounts of hard impermeable surface.
Trees use light energy from the sun to convert carbon dioxide and water into glucose and oxygen.
This process is called photosynthesis. Oxygen is released into the atmosphere through the leaves.
Through the process of photosynthesis, trees remove carbon dioxide, nitrous oxides, sulphur dioxide, carbon monoxide and ozone from the atmosphere.
Trees remove carbon from the atmosphere and store it in their leaves, branches, roots and trunks.
Trees also act as filters to remove particulate matter from the atmosphere.
Particulates that are greater than 2.5 microns and smaller than 10 microns in diameter (PM2.5) are easily inhaled and cause damage to the heart and lungs.
Trees can remove particulate matter from the atmosphere by capturing it on their leaves, contributing to the quality of the environment and public health.
Large urban areas often have higher temperatures than their surrounding rural areas.
This is known as the urban heat island effect and is a recognised problem worldwide. Urban heat islands result from a complex built environment with a high density of human activities.
Trees cool the city and restrict unwanted weed growth in waterways by intercepting ultraviolet rays and transpiring water from their leaves.
Trees manage stormwater ﬂows through their canopies and root systems.
The canopies intercept rainfall, and root systems act like sponges by soaking up water which is then taken up to be used by the tree during its growing processes. The bigger and healthier the root systems the more stormwater is managed.
Healthy trees help reduce the nitrogen, phosphorus and heavy metal content in stormwater. Numerous studies have been undertaken to evaluate the potential for using street trees as elements of a stormwater system.
Trees also reduce erosion by protecting soils from the impact of heavy rain, binding soil on slopes and river and stream margins, and up-taking and processing excess ground moisture.
Trees provide shelter and food for a variety of birds and small animals through their flowers, fruits, leaves, buds, and woody parts. Bacteria and fungi invade the trees causing decay pockets which create nesting sites for some birds and small animals, including native bats.
Decomposing leaves, twigs and non-woody roots increase soil fertility and structure for soil-borne organisms including bacteria, fungi, protozoa, nematodes, arthropods and earthworms.
Trees also provide habitats for other plant life. This includes parasitic plants that live directly off the tree by feeding on it or epiphytes which use the tree as support.
Trees can also create a protective environment that allows the growth of plants that would otherwise not be there e.g. shade dwelling or frost tender plants. Conversely, some trees can also discourage other trees and plants from establishing in close proximity by creating too much shade, using up available nutrients or they may have allopathic qualities.
Trees contribute to overall plant biodiversity as well as indigenous and endemic biodiversity.
Quantifying the economic benefits that trees and other urban forest components deliver can provide sound arguments for deciding whether trees are planted and maintenance budgets are allocated to appropriately manage them. Some of the economic beneﬁts of an urban forest include:
Asphalt streets contain a mix of aggregate, binder, and asphalt cement, which is laid on top of compacted material.
As surface temperature rises, the binder evaporates and breaks down and the surface begins to harden. Surface hardening makes it easier for cracks to form. If not treated small cracks lead to big cracks and allow water to penetrate and weaken the compacted base material beneath.
As the cost of constructing and repairing roads increases, there is a need to protect the City’s investment. Better surface performance translates into reduced maintenance and repair costs and therefore reduces total life cycle costs.
Large shade trees reduced maintenance costs over time when compared to maintenance costs for unshaded road surfaces. Planting large growing trees to create shade also reduces planting costs by up to 50% as fewer trees are required to achieve the desired outcome.
Trees add beauty and character to urban areas by adding colour through their shapes, flowers and foliage, softening hard surfaces, providing shade, shelter and birdlife and generally contributing to the liveability of an area.
Healthy trees planted in streets enhance neighbourhood aesthetics and have been proven to increase property values. It is estimated that properties in tree-lined streets are valued around 30% higher than those in streets without trees.
Studies overseas have demonstrated that a large and well cared for tree canopy within retail and commercial areas promotes positive consumer perceptions and behaviour.
Consumers surveyed in these studies say that they are prepared to travel greater distances to visit a well treed retail or commercial area and are willing to pay more for goods and services than they would otherwise pay at areas that do not have a mature, high-quality tree canopy.
Christchurch is the hub of tourism in the South Island. Visitors are drawn by our Garden City identity. Research shows that ‘The Garden City’ fits with Christchurch’s product and is the most recognised City identity in New Zealand.
The Garden City identity increases our ability to attract business investment as well as visitors, and increase the ‘sense of place’ for residents. Trees in Christchurch support and enhance the Garden City identity. They help promote Christchurch as a destination and in doing this support tourism.
There is a large amount of evidence that now demonstrates that exposure to nature in the form of trees, grass, and flowers offers positive interactions that generate extensive physiological, social, and mental wellness benefits that can help alleviate the burden on national health systems.
In some studies it has been suggested that a view of green space, including trees, can also encourage hospital patient recoveries, reducing the amount of time spent in hospital.
Views of green environments also have an impact on workplace productivity. One study found that workers who did not have a nature view from their desks had 23% more sick leave than those workers who had views of nature.
Because trees are woody biomass they provide an affordable source of renewable energy when harvested. Trees grown for production forestry are sold for export as logs, pulp or processed timber or can be used for carbon credits.
Trees also provide a source for housing materials, furniture, fences, garden structures and ornaments.
Urban trees and vegetation have many positive benefits for the community by providing and allowing daily interaction with nature. Speciﬁc benefits include:
Trees enhance neighbourhood character and identity and the Garden City identity through seasonal colour changes, different shapes, forms, patterns, textures, flowers and seeds.
Trees contribute to the liveability of Christchurch by naturalising and humanising built environments through softening hard surfaces and harsh outlines of buildings, complementing building development, and screening unsightly and undesirable views.
Trees provide thermal comfort to pedestrians and cyclists by blocking harmful UV rays.
It is estimated that a person standing in direct sunlight takes 20 minutes to burn however when standing underneath a tree that provides 50% dappled shade the burn time increases to 50 minutes with a further increase in burn time to 100 minutes for a tree that casts full shade.
Trees also provide shelter from rain and wind.
In the past trees have been viewed as traffic hazards due to their close proximity to the road and their immovability. There have been calls to only plant trees that are frangible – trees that, when mature, only grow to around 100mm in diameter so they will break if hit by a vehicle.
More recently trees and roadside landscaping have come to be seen as aiding traffic and pedestrian safety:
Throughout the ages, trees have fulfilled a number of needs. Trees have been used as sources for food, medicines, toys, cooking utensils, carving, arts and crafts, tools, transport (ships, canoes, and wagons), paddles, dyes, weapons, building materials.
Trees have also been used as symbols or to commemorate historic occasions, special events or people.
Trees have also been used as way finders to guide travellers and as meeting places.
Trees also provide a source for housing materials, furniture, fences, garden structures and ornaments.
Use the Otautahi-Christchurch ecosystem map to find information about the soil types and historic indigenous vegetation of the city. This resource is useful for both backyard planting, school projects and community planting projects.